The present invention generally relates to concrete decks and beams and more particularly toward a system of seismic retrofit for mechanically connecting such decks and beams.
Currently, many buildings and particularly parking structures are built with concrete post and beam construction methods. In such methods, concrete vertical posts support horizontal concrete beams. In many instances, the posts and beams are pre-cast off site and delivered. The posts are formed with ledges that support the beams through typical concrete attachment methods. The beam may be formed with pre-stressed cables running the length thereof that add extra structural integrity and strength.
Once the beams have been secured to the posts, a concrete deck is formed over the beams through conventional concrete construction techniques. In order to mechanically connect the beam to the deck, vertical, metal studs are placed between the deck and the beam. The studs are placed within the beam either during formation of the beam or epoxied into bores formed in the beam after the beam has been fabricated. After the concrete deck sets, the deck is mechanically attached to the beam because the studs are encapsulated by the concrete deck. Such attachment creates a beam and deck system that meets current seismic safety standards.
However, over time, the deck will begin to develop stress fractures due to the movement of the beam. Specifically, when the building is a parking structure, the weight of moving vehicles will cause the pre-cast concrete beam to flex. The flexure of the beam causes stress cracks in and around the metal studs connecting the beam to the deck. Such stress cracks are undesirable because they degrade the structural integrity of the beam and deck system. When the stress cracks form around a metal stud, the mechanical attachment between the deck and the beam may not meet current seismic safety standards. Therefore, the mechanical connection between the deck and the beam must be corrected in order to meet current building codes.
The present invention addresses the problem of retrofitting existing concrete structures by providing a method of retrofit that is quick and inexpensive. The present invention provides a retrofit system for a concrete beam and deck that mechanically connects the two members together such that the structure meets current seismic safety standards.